Responses of Purkinje cells in cerebellar cortex and neurons in the cerebellar nuclei receiving projections from forelimb are being studied in awake, performing cats and monkeys. In particular, climbing fiber and single spike responses in Purkinje cells are being correlated with various parameters of locomotion in cats, including forelimb footfall and lift off and flexor and extensor EMG. Similar single neuron responses are being correlated with forearm movement in monkeys during complex forearm movements.